A. Field of the Invention
This invention relates to brake beams, and more particularly to a strut having a reversible fulcrum for using in brake beams of railway cars, which can be changed, from a left strut to a right strut.
B. Description of the Related Art
There are well known brake shoe assemblies for railway cars by which a brake shoe is pressed against a wheel in order to decrease or stop the rotational speed of the wheel and railway car.
Generally, the brake shoe assembly is held by a structure called brake beam mounted transversely in the bogie of a railway car.
The brake beam generally comprises a compression member, a generally "V" shaped tension member having its ends coupled to the ends of the compression member, a brake shoe linked to the each end of the compression member, and a strut welded to the compression member and tension member, so that the strut remains between the tension and compression members. Said strut is linked to a lever, which applies a force in order to press the brake shoe against a wheel.
Because of the rigidity of this welded structure, several problems come up during normal use.
The lever-strut assembly is supposed to work at a 400 angle rigidly, however due to small gaps between components and undesirable forces produced by the railway car movements during running this angle normally varies few degrees, inducing high torsional moments over the strut and the lever itself. This dangerous and harming forces are translated to the compression and tension members, trough the whole brake beam, causing cock and wedge strengths when brakes are applied and a high wear of the lever-strut assembly components, making necessary a frequent maintenance.
Furthermore, depending on the orientation in which the brake beam is mounted in the bogie, it is necessary to provide right struts or left struts, and if a bogie uses more than two brake beams then right struts and left struts are also necessary.
Therefore, sometimes it is highly desirable that the strut could be able to be changed from a left strut to a right strut, which is impossible with the actual welded strut.
Considering the above referred problems, applicants developed a strut having a reversible fulcrum, which allow the strut to be converted from a left strut to a right strut or vice versa by rotating the main body of the strut around its own axis, making the strut reversible.
The invention is then referred to a strut having a reversible fulcrum, for using in brake beams of the type comprising: a compression member having a first and a second end; a "V" shaped tension member having a central apex, a first end coupled to the first end of the compression member, and a second end coupled to the second end of the compression member; a brake shoe linked to the each end of the compression member; and a strut, wherein the strut comprising: a pipe having a first end and a second end having a surrounding wall, a central slot passing through the surrounding wall at a side portion thereof and an off-center pinhole passing through the surrounding wall at a front portion thereof; a hollow bell joint, having a dome rotary coupled to a central portion of the compression member and a tubular open end at which the first end of the pipe is coupled; and a crown joint having a first end including an internal annular border, rotary receiving the second end of the pipe, and a second end having retaining means to be coupled to the central apex of the tension member.
In this way, the reversible fulcrum allows the strut to "follow" the lever's angular motion by oscillating about its own axis, releasing the torsional moment, which disappears. This feature allows the strut to work always in the same angular position as the lever, without generating reaction moments.
Another benefit of the strut having a reversible fulcrum of the present invention is that a lower wearing in the strut is achieved because of the lower contact forces between lever and strut, reducing considerably the maintenance costs, and the cock and wedge at the.
And last but not least, the reversible fulcrum allows to change the orientation of the brake beam, simply by rotating the off-central pinhole to change the strut from a right strut to a left strut and vice versa.